White spaces, angry faces: Inside the battle over ‘interference’

High stakes

Every city in the country—even New York City—has a host of unused TV channels. Opening up that fertile field of spectrum to the seeds of innovation is a worthy-sounding goal that everyone can agree to in principle, but when it comes down to making the rules that govern access, and to certifying the devices that can operate, the debate hops on the express train to Nastytown.

So say the broadcasters

How did a campaign to allow unlicensed access to TV "white spaces" turn into a "campaign of fear," a "political proceeding," and a series of "ridiculous assertions"? Because of what's at stake.

I sat down recently with several of the leading voices in the white spaces debate. The goal: to get beyond the political posturing in order to present the technical issues being argued about in Washington. What quickly became apparent is that the two aren't so simple to separate.

Black, white, or gray?

Despite the ferocity of the debate over mobile white space devices, one thing that becomes clear in talking to the participants in the conflict is that the issue isn't just a black-and-white engineering challenge. It's much more a calculation of risk vs. reward, except that in this game, the incumbents stand only to lose (from interference), while the new entrants stand only to win (by selling devices and creating more demand for their online services).

No wonder the broadcasters have dug in deeper than World War I trench fighters; in their view, the stability of broadcast TV is at stake, with little upside for them should the experiment go bad.

Take the question of spectral availability. While this might seem one of the easiest to settle—is more than half of US TV spectrum lying fallow or is it not?—the answer isn't obvious. The New America Foundation, a think tank that supports white space devices, claims that 25 to 80 percent of TV bandwidth is unused, depending on where you look. When the group hosted Google co-founder Larry Page at a DC event a few months back, Page also spoke of all that prime spectral real estate that was being "wasted."

But hold on a minute, says that National Association of Broadcasters. We spoke with the group's Senior VP of Science and Technology, Lynn Claudy, who told us that determining spectrum "availability" wasn't a simple task. "You can't just look at a channel lineup for a community, see that half the available channels are empty, and say that the white spaces are wide open," he said. (The group has an entire website devoted to pitching the idea that white space devices will create "interference zones.")

Instead, making the calculation is a matter of setting thresholds that have as much to do with politics as engineering. Because radio frequency signal propagation can "vary wildly over time," especially as one gets farther from the transmitter, the question really becomes, says Claudy, "How reliable do you want the signal to be at what percentage of time?"

The broadcasters want over-the-air signals to be bulletproof, without the slightest danger of being interfered with. After all, the signal is the bread, butter, jam, cup, plate, and silverware of local TV stations; if transmissions are fuzzy, snow-covered, or otherwise interference-laden, people won't watch and ad revenues will drop.

According to Claudy, when you factor in the reliability that broadcasters want to see, urban areas are actually "pretty clogged up." In major cities, interference possibilities become "to us more risky than we would want to see."

Ed Thomas, a former FCC chief engineer who now advises white space backers, like the Wireless Innovation Alliance, says the reality is that there is "a lot of vacant stuff out there," especially in rural America.

And Sascha Meinrath of the New America Foundation calls the entire spectrum availability issue "absolutely ridiculous." The spectrum is only booked up, he notes, if the FCC rules out sticking a white space device on an empty channel adjacent to a TV channel. In fact, so concerned is the broadcasting industry about interference that it has asked for a "third adjacent" rule on white space devices, should they be allowed; a device would need two empty channels on either side of its transmission channel before it could broadcast (for a total of five empty channels).

The issue is tremendously important. If white space devices truly need to find three (next adjacent) or five (third adjacent) available channels before transmitting, their usefulness would be curtailed dramatically.

To see if interference was a concern, the New America Foundation's Wireless Future Program commissioned a study from the University of Kansas Information and Telecommunication Technology Center (ITTC). Sounds technical and science-y, right? Onward, empiricism! How could anyone argue with the results?

But when the report came out in early 2007, "argument" is exactly what happened. Lynn Claudy says that the NAB looked at the report, and the broadcasters approved of its message that "you must have protections for the adjacent channel." If you don't, there's the risk of interference to at least some of the millions of over-the-air TV receivers out there.

Meinrath, of the New America Foundation, was incredulous when I read him the quote. "He lied to you," he said. New America, which commissioned the report, had numerous conversations with the University of Kansas researchers, and Meinrath remains convinced that he understands the report perfectly. Its conclusion, he says, is exactly the opposite: properly designed devices of 100mW or less did not cause interference to TV signals on adjacent channels during the testing.

When the two sides can't even agree on how to read the results of a technical report, it's obvious that no mere survey, study, or test can, on its own, put the issue to rest. But that doesn't mean that the engineering details aren't important; convincing the FCC's engineers, at least, becomes a crucial part of the entire campaign.